External hydraulic pump for motor vehicle transmission

ABSTRACT

This invention pertains to a motor vehicle having a standard drive train including an engine, a torque converter and a transmission, in which the hydraulic fluid required for proper operation of the torque converter and transmission is supplied by an externally mounted, electrically operated pump, with associated fluid storage tank and heat exchanger and requisite fluid circuitry. The torque converter may be offset from the central axis of the engine and transmission, and driven in the offset position by mechanical means, such as a chain or gearing.

CROSS REFERENCE TO RELATED APPLICATION

The provisional patent application entitled “EXTERNAL HYDRAULIC PUMP FOR MOTOR VEHICLE TRANSMISSION” which was filed on May 8, 2007, and granted Ser. No. 60/924,293, is hereby incorporated by reference in the present application.

TECHNICAL FIELD

This invention relates to a motor vehicle with a transmission and torque converter, and to an external electric pump for supplying of high pressure hydraulic fluid to the torque converter for proper operation, and low pressure hydraulic fluid to the transmission for lubrication. This pump may be used with both a standard transmission with clutch and torque converter as well as an automatic transmission with torque converter and no clutch.

BACKGROUND OF THE INVENTION

With ever-increasing oil prices, improving the efficiency of the engine and transmission is a high priority for all motor vehicle manufacturers. Most engines now utilize fuel injection for improved efficiency over previously used carburetors, and the latest induction and exhaust systems have increased fuel mileage significantly.

The use of torque converters in motor vehicle transmissions is well known. The torque converter acts as a torque multiplier and speed differential mechanism between the engine and the transmission. The fluid coupling of the torque converter dampens the application of power from the engine to the transmission, and allows smoother operation of the vehicle. Torque converters are commonly used in automatic transmissions, but they may also be used with manual transmissions, and particularly with a modern dual clutch manual-type transmission.

Originally, mechanical pumps were used to provide pressurized hydraulic fluid to torque converters due to their inherent reliability advantages over such alternatives as electric pumps. Since the mechanical pump required a direct mechanical connection to a power source such as a turning shaft or the like, these pumps were located within the transmission or torque converter housing to allow this connection to be made without external shafts and seals being required.

Disadvantages of mechanical pumps include the fact that they will not function unless the engine is running, and as engine-driven accessories, they rob power from the engine during use. Additionally, the internal pump can be damaged if the pump ingests metal particles resulting from normal wear inside the transmission, or particles resulting from a small part partially disintegrating within the transmission, as frequently happens in high mileage transmissions.

The pump currently located inside the transmission requires that the transmission be completely removed from the vehicle for any pump service or repair. This repair is labor-intensive, and therefore expensive for the vehicle owner.

BRIEF SUMMARY OF THE INVENTION

Over the years electric pumps have improved in reliability to equal that of their mechanical counterparts, erasing that disadvantage versus a mechanical pump. Since no mechanical connection is required for driving the electric pump, there is also no need for the pump to be located within the transmission housing. Being electrically driven, the inventive pump does not require that the vehicle engine be running to maintain fluid pressure and operational readiness, since electrical power for the pump is available from the vehicle storage battery with the engine running or not. With the increasing popularity of hybrid cars and engine-off-at-stops for fuel conservation, an electric pump offers the ability to operate on demand, regardless of vehicle engine operating conditions. Thus, the transmission and torque converter can be pressurized and fully operable even when the engine is not running.

This invention provides an electrically driven pump for providing high pressure hydraulic fluid to a motor vehicle torque converter and low pressure hydraulic fluid for lubrication of the transmission. Since the pump is not mechanically driven, it is not necessary that it be housed within the transmission or torque converter housing. It is advantageous that the pump be located outside the transmission housing, simplifying transmission construction, and allowing faster service and repair and reduced service and repair costs. This also allows the transmission to be more compact in design, since the transmission housing does not have to be enlarged to house the pump or fluid storage tank or sump.

In the preferred embodiment, the electric pump is mounted wherever space permits near the transmission within the vehicle engine compartment. Optimal locations may vary depending upon vehicle design. Front wheel drive automotive designs may dictate that the pump location be in the area of the firewall ahead of the windshield, for example. Rear wheel drive automotive designs may dictate that the pump be located along the inner fender skirt near a front wheel or wherever space permits. A real advantage of the invention is that the pump may be located where space permits alongside the engine or transmission. The pump draws transmission fluid from a storage tank holding a few quarts of fluid and send it through the torque converter and transmission. Fluid leaving the torque converter is directed through a heat exchanger for cooling and returned to the storage tank. Any excess fluid in the transmission is directed back to the pump and then to the storage tank for recirculation. Removing excess fluid from the transmission housing also improves transmission efficiency, eliminating power loss due to the drag on mechanical parts caused by excess fluid normally contained in a wet sump transmission.

The external pump design will make a significant improvement in operating efficiency and operating economy. Fuel mileage increases in the range of 20% to 50% may be expected depending on application, vehicle weight, engine displacement and other variables.

Any type of electric pump will work for this invention, including, but not limited to, vane, spur gear, gerotor, piston, centrifugal or turbine pumps.

Any type of prime mover can be used with this invention, whether it is a gasoline engine, diesel engine, hydrogen engine or power plant, electric motor or a hybrid powered vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the invention as applied to a front wheel drive motor vehicle with a first preferred hydraulic circuit.

FIG. 2 shows the invention as applied to a front wheel drive motor vehicle with a second preferred hydraulic circuit.

FIG. 3 shows the invention as applied to a front wheel drive motor vehicle with a third preferred hydraulic circuit.

FIG. 4 shows the invention as applied to a front wheel drive motor vehicle with an offset torque converter.

DETAILED DESCRIPTION OF THE INVENTION

The preferred embodiments of the invention as illustrated in the drawings show an externally mounted electric pump mounted in the engine compartment near the engine and transmission of a motor vehicle, and not mounted within the transmission or torque converter housing. A high pressure fluid supply line runs from the pump to the torque converter in the bell housing which surrounds the torque converter. This provides the pressurized hydraulic fluid necessary to operate the torque converter and transmission and to lubricate the necessary parts therein. Once the fluid is used by the torque converter and transmission, it is withdrawn from the transmission housing and passed through a heat exchanger for cooling and returned to the storage tank which serves as the supply for the electrical pump.

Depending on main pump location, an external low pressure fluid transfer pump may be needed to move fluid from the transmission to the main external pump. The main pump may be of two-stage or three-stage design, allowing both high and low pressure fluid pumping to be supplied by a single pump.

The preferred embodiments of the invention will be described with relation to the most common application, front wheel drive motor vehicles. Transmission type is not critical to the invention, but the most likely types include a dual clutch manual-type transmission and a fully automatic clutchless transmission. These choices are for illustrative purposes only, and are not meant to limit the scope of the invention, which works equally well with rear wheel drive applications.

For the purpose of describing the preferred embodiments illustrated in the drawings, all high pressure hydraulic lines are shown as dot-and-dash lines, and all low pressure hydraulic or lubricating lines are shown as solid lines. The arrowheads placed at the downstream ends of these hydraulic lines indicate the direction of flow for the fluid within the lines. These conventions hold for all of the drawing figures.

Referring now to FIG. 1, a front wheel drive schematic is shown. Engine 2 is connected to transmission 4 through torque converter and clutch pack 3. Power output from the transmission 4 is delivered by appropriate gearing to the axle shafts 9. Hydraulic fluid is drawn from storage tank 8 through the low pressure line interconnecting it to externally mounted electric pump 7, which pressurizes the fluid and delivers it to the torque converter 3 through a high pressure line and then to other transmission parts 4 requiring lubrication through a low pressure line. Once the fluid has passed through the torque converter, it is delivered via high pressure line to radiator/fluid cooler 1, and then returned to storage tank 8 for recirculation to the external electric pump 7. The low pressure fluid sent to the transmission 4 is returned directly to storage tank 8 via a low pressure line.

FIG. 2 shows a similar schematic for a front wheel drive vehicle with engine 2, torque converter 3, transmission 4 and drive axles 9, but with a different hydraulic fluid circuit. In this case, a third stage has been added to electric pump 7 to facilitate cooling of the heated hydraulic fluid which has passed through the torque converter 3 and transmission 4. Electric pump 7 feeds both high pressure fluid to the torque converter 3 and low pressure fluid to the transmission 4 for lubrication. The high pressure fluid supplied to the torque converter 3 is bled off into the transmission 4 after it has performed its function within the torque converter, and a single low pressure return line delivers the fluid back to the electric pump. This heated fluid is then delivered by low pressure line to radiator/cooler 1, and returned to storage tank 8 for recirculation.

FIG. 3 includes the same engine 2, torque converter 3, transmission 4 and drive axles 9, but provides another different hydraulic circuit for the invention. Like FIG. 1, electric pump 7 draws fluid from storage tank 8 and delivers it to torque converter 3 under high pressure. Fluid leaving the torque converter 3 under high pressure is routed to radiator/cooler 1 and then returned to the storage tank 8. However, the low pressure fluid delivered by electric pump 7 to transmission 4 is returned directly to electric pump 7. A low pressure bleed circuit is provided to return excess fluid to the storage tank 8.

The embodiment of FIG. 4 is unique in providing an offset torque converter 3, which allows mounting of electric pump 7 directly to an external wall of the torque converter housing. This simplifies the hydraulic circuit by feeding high pressure fluid directly to the torque converter 3 without using a separate high pressure line. Like FIGS. 1 and 3, the high pressure fluid which passes through the torque converter 3 is delivered to the radiator/cooler 1 and returned to storage tank 8 for recirculation. Low pressure lubricating fluid delivered by electric pump 7 to transmission 4 and gearing for drive axles 9 is returned by low pressure line directly to storage tank 8 for recirculation.

In this offset torque converter embodiment of FIG. 4, the connection between the torque converter and the transmission may be by chain or gearing if a direct connection is not possible. The offset location of the torque converter also simplifies incorporation of a clutch between the torque converter and the transmission, which may be desirable in some drive train designs.

In describing the four designs illustrated in the drawings, the transmission elements are assumed to require lubrication from an external source, as illustrated by the storage tank and electric pump utilized to feed fluid to both the torque converter and the transmission. The invention would also work if the transmission was of a sealed, self-lubricating type, in which case the fluid lines to and from the torque converter would remain as shown, but the fluid lines to and from the transmission would not be necessary.

Although the present invention is described with reference to the specific embodiments noted above, changes and modifications of the invention may become apparent to those skilled in the art without departing from the spirit and scope of the invention, which is limited only by the appended claims. 

1. In a motor vehicle having an engine, an electrical system including a source of electrical energy, a transmission and a torque converter, said transmission and torque converter being operated and lubricated by pressurized hydraulic fluid, an electrically operated pump located externally of said transmission and torque converter for supplying said pressurized hydraulic fluid to said transmission and torque converter as required for proper operation and lubrication, the hydraulic circuit for said electric pump including a storage tank of sufficient fluid capacity to operate said transmission and torque converter, means for delivering said fluid from said electric pump to said transmission and torque converter, means for returning said fluid from said transmission and torque converter to a heat exchanger to cool said fluid, and means for returning said fluid from said heat exchanger to said storage tank for recirculation to said electric pump and through said transmission and torque converter.
 2. An electrically operated pump and hydraulic circuit as claimed in claim 1, in which said transmission is a fully automatic clutchless transmission.
 3. An electrically operated pump and hydraulic circuit as claimed in claim 1, in which said transmission is a dual clutch manual-type transmission.
 4. In a motor vehicle having an engine, an electrical system including a source of electrical energy, a transmission and a torque converter offset from the major central axis of said engine and transmission and driven by appropriate mechanical means in said offset position, said transmission and torque converter being operated and lubricated by pressurized hydraulic fluid, an electrically operated pump located externally of said transmission and torque converter for supplying said pressurized hydraulic fluid to said transmission and torque converter as required for proper operation and lubrication, the hydraulic circuit for said electric pump including a storage tank of sufficient fluid capacity to operate said transmission and torque converter, means for delivering said fluid from said electric pump to said transmission and torque converter, means for returning said fluid from said transmission and torque converter to a heat exchanger to cool said fluid, and means for returning said fluid from said heat exchanger to said storage tank for recirculation to said electric pump and through said transmission and torque converter.
 5. An electrically operated pump and hydraulic circuit as claimed in claim 4, in which said transmission is a fully automatic clutchless transmission.
 6. An electrically operated pump and hydraulic circuit as claimed in claim 4, in which said transmission is a dual clutch manual-type transmission. 